Matt ayman frames

Redo of the merge of Frame, RigidFrame, FixedFrame, Station and Marker ModelComponents along with code to convert Marker to new format for serialization/deserialization and inclusion of FrameSet in model.
@sherm1 @msdemers @aseth1 or @chrisdembia Please review and let us know your feedback.
A Body is a RigidFrame. A RigidFrame doesn't have to be fixed to an OpenSim::Body. For example in my shoulder Joint I have internal mobilized bodies that I do not expose as Bodies. I would love to expose Frames to debug my internal transformations. Currently, I have to do this be exposing Simbody default geometry (which is ugly, sorry Sherm!) As the Component builder I should be able to slap on Frames to any MobilizedBody without an OpenSim::Body. Just as a Force has a force index (or indices), a Constraint has underlying constraint indices, the only requirement for a RigidFrame should be that it has MobilizedBodyIndex. This also enables FixedFrame to be implemented by Weld (mobilizer) under the covers, if so desired.